Apparatus for mixing concrete



June 28, 1932. A. KNOWLES APPARATUS FOR MIXING CONCRETE Filed Jan. 27, 1930 INVENTOR. amrkuowu: 4

ATTORNEYS.

Patented June 28, 1932 warren sures PATENT OFFICE ALBERT KNOWLES, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO TRANSIT MIXEBS, INQ, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION 01 NEVADA.

APPARATUS FOR MIXING CONCRETE Application filed January 27, 1980. Serial No. 423,577.

This invention relates to the mixing of concrete material and especially to such mixing in transit of the materials from the place of supply to the place of depositing the mixed concrete.

The objects of the invention are to provide an improved method of mixing concrete whereby the concrete is denser than would be the case otherwise, and also a special arrangement of apparatus units whereby the method may be carried out.

Outline of the inoention.-In the transportation and simultaneous mixing of concrete in the so-called transit mixers, or automobile truck mixers of the general type shown in my copending application for patent filed under Serial No. 406,359 on November 11, 1929, the materials are violently agitated by revolution of the mixing drum during transportation on the truck, and it follows that considerable an is beaten into themixed concrete through the action of the mixing blades and that the jostling of the truck slops the load about to increase the amount of air mixed into the mass. Such imprisoned air when finely divided cannot escape in discharging the load into the forms, for as a rule the time of hauling is such that the concrete is about ready for the initial set at time of discharge and since it has been kept in constant agitation up to this time most of the air is permanently locked within the mass in a fine state of division so that the density and ultimate strength of the concrete is considerably affected thereby.

My invention principally consists in extracting the air from the mass of materials during the mixing thereof. and particularly in carrying out the invention on a portable truck mixer of the type described.

In the drawing accompanying this application the figure is a side elevation of a transit or automobile truck mixer of the revolving drum type with parts broken away to reveal important features, all substantially the same as shown in my copending patent application aforesaid except that it is provided with the special arrangement of exhausting apparatus for carrying the present invention into efect. a

In the drawing the forward end of the truck carrying the engine has been omitted as the invention is confined to features adjacent the drum.

vThe drawing shows at 1 the chassis frame of a motor truck, 2 the rear wheels, 3 the cab, 4 the steering wheel with the usual hand and foot controls below it.

Pivotally mounted at 5 on the chassis frame is an auxiliary or tilting frame 6 upon which is revolvably mounted the cylindrical mixing drum 7 driven from the power of the truck engine by means'of a pinion 8 meshing a gear ring 9 secured to the drum, all in a manner well known so that the drum may be rotated while in the horizontal position or while being tilted on frame 6 for discharge of the load from a door 10 at the rear of the conical end 11 of the drum.

The tilting of the frame 6 with the drum is accompllshed by any form of power truck hoist in the wellknown manner not shown in the drawing as not involved in the present invention. a

The drum is closed at its forward end 12 and the door 10 is arranged to close air ti ht.

Spaced just above the drum is a saddleag shaped water tank 13 supported on channel iron frame members 14 (shown broken) which extend over the drum and are seeured to the tilting frame 6.

The water tank is air tight and provided with a filling plug 15, pressure gage 16, safety relief valve 17, air pressure pi e 18, and

water discharge pipes (one at eac side) 19 for delivering water to the interior of the drum. 4

Water pipe 19 is valved at 20 for easy control of the truck driver and connects to an axial pipe 21 which enters the forward end of the drum through a stufling box 22 in any approved manner so that the drum may revolve about the pipe without admitting air at this point, while within the drum the pipe may be rotatably supported with respect to the drum by one or more of spider arms as indicated at 23.

Water is delivered to the mix through one or more risers or vertical pipes 24 which project upward from pipe 21 and are provided at Bil seen that after loadin elevated as high as possible so as to be above the highest level of material to be mixed and thus avoid clogging of the openings, though they cannot extend much higher than shown for they must clear the drum mixing blades 1 (not shown) which constantly pass over them during the revolution of the drum.

Pipe 21 is relatively large and within it passes a smaller pipe 26 for exhausting the air irom the drum. This pipe 26 comes out of a tight joint 27 either at the side or at the end of pipe 21 and also extends upwardly as at 28 as high as ossible and is provided with a side perforate cap 29 similar to the water pipes.

Air pipe 26 passes out of the outer end of pipe 21 through a tight joint 30 and extends downward to a pump 31 mounted on the tilting frame 6 and driven by any convenient means such as a shaft 32 geared at 33 to the shaft of pinion 8 which drives the drum, while clutches 41-42 provide for the truck driver disconnecting the pump or drum separately when desired.

The discharge of the pump is rovided with a check valve at 34 so it will old the pressure developed and asses through pipe 18 to the water tank, whi e at 35 is a two-way valve for discharging the air directly to atmosphere through outlet 36 when it is not desirek to further compress air into the water tan Pump inlet pipe 26 is provided with a check valve at 37 to automatically hold the vacuum in the drum when the pump is stopped and a small air cock at 38 provides for hrealu attempting to 0 en door 10 for discharge of the concrete. lso provided on pump inlet pipe 26. is a two-wa valve 39 for taking air through 0 on end oi nipple 4.0 when desiring to pump air into the water tank after exhaustion of the drum, and it is manifest that this valve may be an automatic check valve set to open to outer atmosphere when no further suction can be had from the drum, and it is also evident without illustration that a. vacu um gage maybe placed on pipe 26 if desired.

With the arrangement described it will be the drum with concrete materials throng door 10 and sealing the same, the pump may be set in motion to exhaust the drumiwhether or not the drum is revolving, or even during tilting.

If water has been introduced into the drum "together with the other materials, it will not be necessary to compress air above the water in the water tank, and in whichcase valve 20 may be closed, valve 35 turned to open nipple 36 and the air pumped from the tank is exhausted at 36 to atmosphere.

If, however, the dry materials only are loaded into the drum, the tank is filled with eject it into t 'ng the vacuum as is desirable before eonor? water, and the air is first exhausted from the dry materials, from winch it readily escapes, before any water is admitted from the tank, thus insuring a more complete riddance of the air from the interstices of the mass than would otherwise be the case.

The materials may be mixed as long as desired in the vacuumized drum, and 'ust before opening door 10 to discharge t e load the vacuum should be broken by admitting air through air cook 38.

it will be apparent from the above disclosure that minor changes may be made within the scope of the invention without altering the method of operation thereof and that instead of com ressing air above the Water to he concrete, it may be allowed to run from the tank by gravity or pumped therefrom by any manner well known in the art, and therefore I claim:

1. A transit concrete mixer comprising a motor truck, a frame tilt-ably mounted on the truck, a mixing container mounted upon the frame for tilting therewith, an air-tight door for discharge oi the concrete, a pump carried on the frame piped for exhausting the container of air, and means for operating the mixer and pump from the truck engine power.

2. A transit concrete mixer comprising a motor truck, a frame tiltably mounted on the truck, a mixing container mounted upon the frame for tiltin therewith, an air-tight door for discharge 0 the concrete, a pump carried on the frame piped for exhausting the coni tainer of air, and means for operating the mixer and pump simultaneously from the truck engine power.

3. In a structure as specified in claim 1,

means for cutting out the pump as desired a and pump from the truck engine power, and 1 a water tank on the miiger plped to the container for discharge therein, and said pump arranged to pump its discharged air into the water tank to create a pressure therein.

5. transit concrete mixer comprising. a moto truck, a frame tiltably mounted on the truck, a. mixing container mounted upon the ironic for tiltin therewith, an air-tight door for discharge 0 the concrete, a pump carried on the frame piped for exhausting the container of air, means for operating the mixer and pump from the truck engine power, and a water tank on the mixer piped to the container for discharge therein, said pump arranged to pump its discharged air into the water tank to create a pressure therein, and valves on the piping toand from the ump whereby the pump may be made to disc arge either into the tank orvinto the outer air.

6. In a structure asspecified in claim 1, the piping for exhausting the container includmg an air-receiving pipe open within its center.

the container at a point suhstantially abeve ALBERT KNOWLES. 

